In this type of planar storage facility, as described in Japanese Published Unexamined Patent Application No. H7-172762 (Patent Literature 1), the storage/retrieval device is configured so as to correspond to the shape of the storage item and the like, and thus as long as the storage/retrieval device can handle the item, storage items to be stored having various types of planar sizes such as a plastic container of a planar size which can be manually transported can be stored and retrieved in and from a desired position within the storage item placement plane. Then, since this type of planar storage facility is configured such that a storage/retrieval operation is performed by an automatic operation of the storage/retrieval device, the storage/retrieval device is automatically operated such that storage items are stored close together while giving first priority to the storage efficiency as long as a problem in the storage/retrieval by the storage/retrieval device is prevented from being encountered.